Synthesis and characterization of cleavable as well as noncleavable photosensitive heterobifunctional reagents of maximum linking length up to 25 A; the photosensitive group will be phenylazides and N-hydroxysuccinimide or imidate will be the conventional functional groups. Several sulfhydryl specific reagents are also planned. Cleavable reagents will be prepared initially with a disulfide bond, and its position in reagents will be varied in order to increase its stability against potential disulfide exchanges. To synthesize cleavable photosensitive heterobifunctional reagents carrying radioisotopes, in particular at the photosensitive half of the reagents, and to establish ways to label surface receptors with or without permanently crosslinking hormones and receptors. To attach reagents to luteinizing hormone and to characterize activated molecules. To bind the activated hormone to granulosa cells and to identify binding molecules. To determine if binding molecules are receptors.